To suppress the negative edges generated by gradually degrading the magnetic permeability at the end on the side opposite to the magnetic gap layer of magnetic cores the futherer from the magnetic gap layer with respect to the lamination direction of the magnetic gap layer.

The magnetic permeability of the first magnetic core 2 and the second magnetic core 5 is gradually deteriorated toward the end edge 5a of the magnetic core 5 near the end (dotted line part) of the magnetic core 5 on the side opposite to the magnetic gap layer 4 consisting of SiO2, etc., which is a gap material layer. A nitrogen compsn. increases simply with an increase in a nitrogen partial pressure when the magnetic cores are produced by changing the nitrogen partial pressure at the time of sputtering. The nitrogen compsn. decreases when the sputtering electric power under the same nitrogen partial pressure increases. Such decrease arises from the increase in the sputtered atoms of Fe and Ta and the relative decrease in the atom number ratio of N to the Fe and the Ta when the sputtering electric power increases. The adjustment of the magnetic permeability is made possible by controlling the sputtered atom number of the Fa and the Ta constant, thereby controlling the nitrogen compsn. of the sputtered films.